Fibrosarcoma of Bone






  • Just as for osteosarcoma, fibrosarcoma has a preference for the metaphyses of long bones, especially the distal femur, with the proximal femur, distal humerus, proximal tibia, and pelvis following in frequency.




Clinical Symptoms and Signs






  • Local pain and/or the presence of a mass is the usual initial symptom of primary fibrosarcoma of the bone.


  • Limitation of motion of a neighboring joint and pathological fracture can occur in some cases at presentation.


Image Diagnosis



Radiographic and CT Features






  • Imaging methods show a metaphyseal eccentric lytic lesion, with a predominantly permeative pattern, without peripheral or periosteal bone reaction even after cortical permeation and soft tissue extension.


  • There is no sign of mineral deposits or of bone production by the tumor.


  • Geographical, permeative, or “moth-eaten” patterns can probably be related to different histological grades.


  • MRI, and bone scan do not contribute with further data for the diagnosis.


Image Differential Diagnosis



Fibroblastic Osteosarcoma and Low-Grade Central Osteosarcoma






  • These tumors present very scarce or variable bone production that when and if identified by imaging methods can suggest the correct diagnosis.


Desmoplastic Fibroma of Bone






  • Fibrosarcoma shows indistinct borders due to tumor permeation, and expansion of the cortices is unusual.


Malignant Lymphoma of Bone






  • In long bones, it is preferentially situated in the diaphysis. Both lesions can share the “moth-eaten” pattern; other infiltration patterns are more suggestive of fibrosarcoma.


Undifferentiated Pleomorphic Sarcoma/MFH






  • Has no imaging differences in relation to high-grade fibrosarcoma


Pathology



Gross Features






  • Fibrosarcoma presents a white and firm cut surface, with a trabeculated pattern and circumscribed margins.


  • Higher-grade tumors present a more fleshy appearance and focal friable necrotic or hemorrhagic areas.


  • Margins tend to be indistinct.


Histological Features






  • Fibrosarcoma is composed by a uniform spindle cell population arranged in “herringbone” or fascicular pattern.


  • Collagen production is variable and related to tumor grade, high-grade lesions scarcely showing collagen matrix.


  • By definition, there can be no other kind of matrix production except pure collagen to categorize a neoplasia as fibrosarcoma.


  • High-grade lesions also present more frequent mitotic and atypical nuclei as well as occasional areas of necrosis.


Pathology Differential Diagnosis



Fibrous Dysplasia






  • If the sample does not include immature bone trabeculae, it may be difficult to separate, on exclusively histological grounds, from well-differentiated fibrosarcoma.


  • Attention to infiltrated margins on histology and radiological signs of aggressiveness can help in the diagnosis.


Fibroblastic Osteosarcoma






  • Always contains neoplastic bone trabeculae that must be sought extensively in these predominantly fibroblastic tumors


Desmoplastic Fibroma of Bone






  • Has elongated strands of well-differentiated active-appearing spindle cells and is seldom permeative, less cellular, and less atypical than fibrosarcoma; mitoses, when present, are always typical.


Leiomyosarcoma of Bone






  • Spindle cell bundles are disposed at cross angles and present a “schoolfish” pattern different from the herring bone predominant pattern of fibrosarcoma; nuclei are elongated and blunt ended (cigar-shaped).


  • Positive for smooth muscle markers and keratin.

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Jan 2, 2017 | Posted by in ORTHOPEDIC | Comments Off on Fibrosarcoma of Bone

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